Bacterial biofilms beat Teflon in repelling liquids

Slimy mats of bacteria called
biofilms may be the most liquid-repellent materials in nature,
researchers have discovered.

"There are a few manmade materials that can perform better, and
they have to be made in clean rooms. They're incredibly expensive
and brittle," said materials scientist Alexander Epstein of Harvard
University, co-author of the new study. "Making biofilm is as easy
as growing bacteria."

The goo secreted by Bacillus subtilis bacteria not only deflects
water like a lotus leaf, but also repels concentrated alcohol,
acetone and even vaporised liquid, according to a study published
January 18 in Proceedings of the National Academy of Sciences.

Biofilms are communities of bacteria that stick together using a
mixture of sugars and proteins called the extracellular matrix,
which takes on a wrinkled form under powerful microscopes (see
image below). Since the discovery of bacteria in the late 1600s,
most research has covered individual cells. It's only since the
1990s that scientists have begun to understand the pervasiveness
and importance of biofilms.

"We're realising more and more that almost all bacteria in
nature are found as biofilms," Epstein said. "It offers a lot of
advantages for them, including better protection and increased
chances they'll stick to sources of food. It's crazy stuff."

While trying to map the internal structure of B. subtilis
biofilm using a vaporised radioactive tracer that would show up in
x-ray
photos, the researchers found it couldn't get inside. They were
frustrated at first, but Epstein said his team soon realised the
significance of the stubborn biofilm.

"We started to put different liquids on it. Concentrated
alcohols just [beaded up]," Epstein said. For comparison, the
researchers also tried a non-stick Teflon surface. "We found the
biofilms substantially superior to Teflon," he said.

To analyze resistance to wetting, Epstein and his team measured
the angle between droplets of liquid and the materials' surfaces.
At ten per cent alcohol, similar to wine's concentration, Teflon
started getting wet. Biofilms, however, balled up all
concentrations of alcohol up to 80 per cent (similar to Everclear).
Liquids wetted biofilms only after sitting on them for minutes or
hours.

Epstein isn't suggesting we grow biofilms for frying pans or
rain jackets, but thinks the research will inspire practical new
applications. His team ultimately hopes to resolve biofilm's
molecular structure to develop new materials.

"We don't fully understand it, but it's broadly true that you
need both protein and sugars for this repelling property," Epstein
wrote in an email to Wired.com. "Sugars absolutely have to be
there, but we don't know why. We're doing some follow-up research
on that now," he said.

Comments

Wouldn't that fact that bacteria will require the right conditions to exist severly limit it's applications?On the other hand it might make a brilliant waterproofing for gadgets if it can be formed into a gasket